Carpet underlays are installed between the subfloor and the carpet in a flooring system to impart support to the carpet thus improving the stability and increase the life of the carpet. In addition, carpet underlays can improve the softness and cushioning features of the carpet for the comfort of a user. Single layer carpet underlays are traditionally used for both residential and commercial applications. Carpet underlay for residential use is typically a foam pad. The pad is constructed of recycled foam which has been shredded into particles, the particles then formed into a pad and bonded together to form the carpet underlay. While the foam pad is soft, cushioning and resilient, durability aging tests show that over a period of wear the foam loses its resilience and disintegrates, causing the foam to take on a yellowish tint. The bond between the foam particles may also disintegrate, resulting in a carpet underlay which is hard, flat and which may eventually decompose. As a result, in high traffic areas such as in hotels and other commercial applications, fiber pads are traditionally used as single layer carpet underlays. Fiber pads are firmer than foam pads and maintain roughly their original height throughout their life. Fiber pads are also effective bridging materials which provide reinforcement and distribute stress across the carpet to extend the wear life of the carpet. While fiber pads are more durable than foam pads, they are not as soft, cushioning or resilient.
Multi-layer pads are also used as carpet underlays. These underlays typically include a combination of one or more layers of polymeric foam, liner sheets of polyethylene film and re-bonded foam padding. For example, a layer of polyurethane foam is layered between and bonded to a liner sheet of low density polyethylene and a preformed padding material of polyurethane foam or re-bonded foam. Another multi-layered foam underlay comprises a combination liner sheet of polyethylene, one or more polyurethane foam layers and a second polyethylene liner sheet. Other combinations comprise a layer of polyethylene, an intermediate layer of polyurethane foam and a base layer of re-bonded foam.
Conventional processes for making multi-layer carpet underlays include feeding a polyethylene liner sheet onto a conveyor belt and spraying uncured polyurethane foam onto the liner sheet. Preformed foam padding is applied to the uncured polyurethane foam. The composite pad is fed between a pair of heated conveyor belts to cure the polyurethane foam and to adhere the foam to the liner sheet and the foam padding. In another process, a polyethylene liner sheet having a previously cured layer of polyurethane foam material is fed onto a conveyor belt. Uncured polyurethane foam is sprayed onto the cured polyurethane foam layer. Another polyethylene liner sheet is applied to the uncured polyurethane foam to sandwich the cured and uncured polyurethane foam layers between the polyethylene liner sheets. The composite is fed between a pair of heated conveyor belts to cure the polyurethane foam and to adhere the foam to the liner sheets and the previously cured polyurethane foam layer. In a further process for making a multi-layer carpet underlay a first polyethylene liner sheet is fed onto a conveyor belt and uncured polyurethane foam is sprayed onto the polyethylene sheet. A second polyethylene liner sheet is applied to the uncured polyurethane foam. The composite pad is fed between a pair of heated conveyor belts to cure the polyurethane foam and to adhere the foam to the first and second liner sheets.